Targeting molecules involved in TRAIL-mediated signalling has been hailed by many as a potential magic bullet to kill cancer cells efficiently, with little side effects on normal cells. Indeed, initial clinical trials showed that antibodies against TRAIL receptors, death receptor (DR)4 and DR5, are well tolerated by cancer patients. Despite efficacy issues in the clinical setting, novel approaches to trigger TRAIL-mediated apoptosis are being developed and its clinical potential is being reappraised. Unfortunately, as observed with other cancer therapies, many patients develop resistance to TRAIL-induced apoptosis and there is thus impetuous for identifying additional resistance mechanisms that may be targetable and usable in combination therapies. Here, we show that the death-associated protein kinase 2 (DAPK2) is a modulator of TRAIL signalling. Genetic ablation of DAPK2 using RNA interference causes phosphorylation of NF-jB and its transcriptional activity in several cancer cell lines. This then leads to the induction of a variety of NF-jB target genes, which include proapoptotic DR4 and DR5. DR4 and DR5 protein expression is correspondingly increased on the cell surface and this leads to the sensitisation of resistant cells to TRAILinduced killing, in a p53-independent manner. As DAPK2 is a kinase, it is imminently druggable, and our data thus offer a novel avenue to overcome TRAIL resistance in the clinic. Despite the effort and resources invested in cancer research, cancer remains a serious public health problem. Most patients are treated surgically, with chemotherapeutic drugs and/or antibodies and small molecule inhibitors. Patients generally respond well to the initial therapy but frequently develop resistance to it. This poses a challenge to their treatment and calls for alternative approaches to be developed. Indeed, much excitement was generated in the mid-1990s when tumour necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) was identified. [1][2][3][4] TRAIL is a death receptor (DR) ligand that signals through DR4 and DR5, two members of the TNF receptor family. 5-7 DR5 has two isoforms that differ by 29 amino acids and which are functionally indistinguishable. 5,8 TRAIL ligation activates primarily the extrinsic apoptotic pathway. The formation of ligand/receptor complexes leads to the assembly of a multiprotein death-inducing signalling complex (DISC), which in the case of TRAIL is typically composed of the adaptor Fasassociated death domain, caspase-8, caspase-10 and/or c-FLIP. These initiator caspases proteolytically cleave effector caspases such as caspase-3, caspase-6 and/or caspase-7 thereby activating them. This leads to the destruction of key cellular components and the appearance of typical features of apoptosis. TRAIL can also activate intrinsic apoptotic pathways via BID and thus involve mitochondria. By virtue of preferentially killing tumour cells, TRAIL is seen by many as a 'magic bullet' against cancer cells. Some cancer cells, however, are resistant, or develop resistanc...
Background:Endo180 (CD280; MRC2; uPARAP)-dependent collagen remodelling is dysregulated in primary tumours and bone metastasis. Here, we confirm the release and diagnostic accuracy of soluble Endo180 for diagnosing metastasis in breast cancer (BCa).Methods:Endo180 was quantified in BCa cell conditioned medium and plasma from BCa patients stratified according to disease status and bisphosphonate treatment (n=88). All P-values are from two-sided tests.Results:Endo180 is released by ectodomain shedding from the surface of MCF-7 and MDA-MB-231 BCa cell lines. Plasma Endo180 was significantly higher in recurrent/metastatic (1.71±0.87; n=59) vs early/localised (0.92±0.37; n=29) BCa (P<0.0001). True/false-positive rates for metastasis classification were: 85%/50% for the reference standard, CA 15-3 antigen (28 U ml−1); ⩽97%/⩾36% for Endo180; and ⩽97%/⩾32% for CA 15-3 antigen+Endo180. Bisphosphonate treatment was associated with reduced Endo180 levels in BCa patients with bone metastasis (P=0.011; n=42). True/false-positive rates in bisphosphonate-naive patients (n=57) were: 68%/45% for CA 15-3 antigen; ⩽95%/⩾20% for Endo180; and ⩽92%/⩾21% for CA 15-3 antigen+Endo180.Conclusion:Endo180 is a potential marker modulated by bisphosphonates in metastatic BCa.
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